Face seals are used in gas turbine engines to prevent the leakage of fluid along rotating shafts where the shaft extends through a stationary structure such as a wall or partition. Referring to FIG. 1, a typical face seal is comprised of a stationary stator 22, having a flat surface 25 that rubs against a flat surface 17 of a rotating rotor 20. The rubbing of these surfaces generates significant amounts of heat and as a result high temperatures and thermal gradients within the rotor 20. These thermal gradients must be managed to prevent failure of the seal. A major contributor to this adverse thermal reaction in many seals is a lack of adequate means for carrying excess heat away from the rotor. When the thermal load of the seal is not managed, the formation of coke (burned oil) at the sealing flat surface 25 can occur. Also, the adverse thermal gradients cause the flat surface of the rotor 20 to swing away from the flat surface of the stator 22 resulting in leakage.
One approach to this problem has been to make the rotor from ceramics. A disadvantage of ceramics is their brittleness. A related disadvantage of ceramics is the need for sophisticated and often complex schemes for mounting the ceramic rotor, due both to the brittleness and to the low thermal growth of ceramic. Another approach to this problem has been to provide external cooling of the rotor 20 in the form of oil jets. Yet another approach is to internally cool the rotor using coolant passages, as for example in U.S. Pat. No. 2,990,202 issued to W. T. Dennison on Jun. 27, 1961. In Dennison, oil from inside a shaft enters the inner diameter portion of a seal rotor and flows through passages defining a labyrinth path to an outer diameter surface where the oil is discharged. However, these approaches add significant complexity to the design of the rotor, are expensive, and are not always practical due to space limitations.
Accordingly there is a need for an inexpensive oil cooled face seal configured to dissipate heat from the rotor in the most efficient manner when subjected to high thermal loads.